Nanoporous Carbon-based CO2 Reduction Catalysts: Exploring the Combined Effects of Surface Chemistry and Porosity

For the first-time sulfur-doped, nitrogen-doped and sulfur, nitrogen-codoped nanoporous carbons were systematically studied as catalysts for CO2 electrochemical reduction reaction (CO2ERR). The Faradaic efficiencies (FE) of CO and CH4 formation were calculated to evaluate the performance of these carbons. The best catalysts showed the FE of CO and CH4 formation of 29% and 0.76%, respectively. It was found that the overall performance in CO2ERR dramatically increased upon the reduction pretreatment of the carbons in N2-saturated electrolyte before the CO2 reduction process. The pretreated carbon showed the maximum FE of CO and CH4 formation of 39% and 1.2%, respectively. The most stable carbon showed the unchanged FE of CO formation for 48h, which was followed by a gradual decrease in the FE up to 96h. The performance of CO2ERR was affected by such carbon surface features as the type and number of functional groups, electric conductivity, porosity and surface acidity/basicity. Positively charged carbons induced by pyridinic-N, quaternary-N and thiophenic-S were identified as catalytically active groups. The reduction process intermediates CO2/COOH* were stabilized on these positively charged sites. The pyridinic-N induced positively charged carbon showed the highest activity for CO formation. It was found that the carbon surface suffered from some extent of oxidation after CO2ERR. The pyridinic-N was oxidized to pyridonic-N. However, when pyrazinic-N was present on the carbon surface, the pyridinic-N remained stable and pyrazinic-N was found to be decomposed after CO2ERR. This indicates that pyrazinic-N was a sacrificial species protecting the active pyridinic-N sites from oxidation during CO2ERR, which markedly increased the stability of the catalysts. A high electric conductivity of catalysts is a necessary factor for the desirable performance in CO2ERR. Porosity is a predominant factor for CH4 formation but not for CO formation. However, it increases the adsorption strength of CO2 and intermediates and thus enhances the electron transfer. The pores, especially the ultramicropores, which provide high adsorption potential, bind CO strongly. The adsorbed CO (intermediate CO*) likely accepts both electrons and protons simultaneously and thus CH4 is formed. Acidic surface also helps with the protonation of CO*, which is beneficial for CH4 formation. The basic surface of carbon favors CO formation since its basic feature suppresses the competing hydrogen evolution reaction. The mechanism of CH4 formation might not be an exclusively electrochemical process. With the existence of formed H2 and CO that are adsorbed in the pores, the system might act as a set of Fisher-Tropsch nanoreactors where CH4 is formed. Sulfur-containing nanoporous carbons also showed photoactivity when exposed to visible light during CO2ERR. It was found that the band-gap decreased with the increase in the amount of thiophenic-S on the surface and an increase in the contribution of sp2 configuration. These features were indicated to be responsible for the generation of photocurrent under visible light. The photoinduced electrons were accepted by CO2 and the partial current density for CO formation increased. The study sheds new light on developing nanoporous carbon as metal-free catalysts for CO2ERR. The results obtained suggest that these materials have a potential be a low-cost alternative to the metal electrocatalysts. The investigated process is environmental friendly and economical. These findings also extend our understanding of the mechanism of CO2ERR. Further studies on improving the efficiency of CO2ERR in nanoporous carbons are needed. This can be achieved by exploring the diversity of their surface modifications

Contributing to Engineering Colleges Students\u27 Development Through Out-of-Class Involvement: A Survey of Chinese Private Colleges\u27 Engineering Students

The purpose of this study was to investigate the primary characteristics of engineering college students’ involvement in out-of-class activities (OA) at one private college in China through the use of the translated and culturally adapted Chinese version of the Postsecondary Student Engagement Survey (PosSES 2.1). This study provides the statistical analyses of the survey data completed by 283 senior engineering students on their perceptions about their levels of involvement related to positive/negative outcomes students perceive and affective engagement. Data results showed all levels of involvement have a significant influence on positive outcomes. Besides, active involvement degree, hours, and types of OA have significant differences in engineering students’ affective engagement. Only the number of OA in which students were involved has a significant influence on negative outcomes and had no difference for affective engagement. Moreover, results reported a strong correlation between affective engagement and positive outcomes. These findings confirmed the importance of participation in OA and indicated paying attention to the quality of OA involvement other than the quantity was essential for colleges and universities, educators and policymakers, and engineering undergraduates. Furthermore, this study provides descriptive statistics on participants’ reported data on identifying incentives for and barriers to out-of-class involvement. To date, existing Chinese literature has primarily focused on student engagement and learning outcomes. However, this study provides evidence that OA involvement is a practical pathway to Chinese engineering college students’ development and makes affective engagement a significant contributor to student engagement measures in engineering education. Significantly, the PosSES 2.1 (Chinese version) that measures different facets of engineering students’ out-of-class engagement meets the urgent need of Chinese higher education to investigate and understand the status quo of engineering students’ OA involvement. Additionally, this study provides new insight for educators and policymakers to analyze the reasons for problematic out-of-class involvement that could help them design meaningful OA and create new approaches to mitigate the crisis of engineering undergraduates’ low retention rate and persistence. Future researchers should consider exploring more complex dimensions and broaden the research perspective in this area

EXPERIMENTAL STUDIES ON THE DETERMINATION OF ACOUSTIC BULK MATERIAL PROPERTIES AND TRANSFER IMPEDANCE

Soft trim absorbing parts (i.e., headliners, backwalls, side panels, etc.) are normally comprised of different layers including films, adhesives, foams and fibers. Several approaches to determine the complex wavenumber and characteristic impedance for porous sound absorbing materials are surveyed and the advantages and disadvantages of each approach are discussed. It is concluded that the recently documented three-point method produces the smoothest results. It is also shown that measurement of the flow resistance and the use of empirical equations is sufficient for many common materials. Following this, the transfer impedance of covers, adhesives, and densified layers are measured using an impedance difference approach. The transfer matrix method was then used to predict the sound absorption of a multi-layered materal which included a perforated cover, fiber layers, and an adhesive. The predicted results agree well with measurement

Targeting the complex I and III of mitochondrial electron transport chain as a potentially viable option in liver cancer management

Abstract Liver cancer is one of the most common and lethal types of oncological disease in the world, with limited treatment options. New treatment modalities are desperately needed, but their development is hampered by a lack of insight into the underlying molecular mechanisms of disease. It is clear that metabolic reprogramming in mitochondrial function is intimately linked to the liver cancer process, prompting the possibility to explore mitochondrial biochemistry as a potential therapeutic target. Here we report that depletion of mitochondrial DNA, pharmacologic inhibition of mitochondrial electron transport chain (mETC) complex I/complex III, or genetic of mETC complex I restricts cancer cell growth and clonogenicity in various preclinical models of liver cancer, including cell lines, mouse liver organoids, and murine xenografts. The restriction is linked to the production of reactive oxygen species, apoptosis induction and reduced ATP generation. As a result, our findings suggest that the mETC compartment of mitochondria could be a potential therapeutic target in liver cancer

Mechanical performance evaluation of fiber composites equipped with In-Situ wireless sensor bodies

In modern day structural engineering, fiber-composites play a vital role for their capability for light-weight construction and high stiffness value. More and more applications are being developed in various industries ranging from science, architecture and engineering. These structures can also be equipped with multi-component sensor systems for different performance evaluations both during pre- and post-curing processes. In this work a novel method is developed to place wireless sensors inside the fiber reinforced composite system to enable multifunctionality without much trade-off in mechanical performance. Key objective here was to optimize the sensor shape to minimize stress accumulation and crack propagation around the sensor geometry inside the cured composite sample under stress. A finite element simulation model is developed for this purpose and a parametric model for the sensor geometry provided better insight into the force distribution along the fibers around the sensor element. Consequently, different testing sample combinations were prepared, for which, fibers were either cut or bend around the sensors and dielectric channels. Various composite samples with different shapes of sensor dummies were also experimentally tested to validate the computational results. CT scan models of post-cure samples before and after loading enabled in-depth understanding of fiber alignment that could cause disturbances in overall mechanical performance. The scan models also provided with sufficient information about unwanted porosity, and micro-crack growth inside the composite under loading, which turned out to be vital for establishing a reliable simulation model and improving parameters in manufacturing process. In the end, the goal of the work was to transport the know-how of such production unit from experimental and flexible manufacturing system like vacuum assisted resin infusion (VARI) to more sophisticated processing systems like prepreg manufacturing where all necessary information can be provided as inputs prior to the impregnation, thus removing error occurred due to manual handling

Spontaneous pregnancy after tracking ovulation during menstruation: A case report of a woman with premature ovarian insufficiency and repeated failure of in vitro fertilization

The diagnosis of premature ovarian insufficiency (POI) is devastating in women of reproductive age because of the small chance of spontaneous pregnancy. Here, we report a very rare case with POI and repeated failure of in vitro fertilization (IVF) where the final result was natural fertilization following guidance to have sexual intercourse during menstruation as ovulation was monitored. Estradiol valerate was used to increase the thickness of the endometrium and stop the menstrual bleeding. There was a serum level of 208.44 IU/L of human chorionic gonadotropin (HCG) 14 days after the ovulation. Later, a series of transvaginal ultrasounds also indicated a normal-appearing intra-uterine pregnancy. A healthy baby girl was delivered at term by means of cesarean section. Our report suggested that although the chance of spontaneous pregnancy is relatively low in patients with POI with repeated IVF failures, as long as ovulation does occur, even if it happens during menstruation, natural pregnancy is still worth trying with a series of proper and personalized treatments

Functional traits and environment jointly determine the spatial scaling of population stability in North American birds

Understanding the spatial scaling of population stability is critical for informing conservation strategies. A recently proposed metric for quantifying how population stability varies across scales is the invariability-area relationship (IAR), but the underlying drivers shaping IARs remain unclear. Using 15-year records of 249 bird species in 1035 survey transects in North America, we derived the IAR for each species by calculating population temporal invariability at different spatial scales (i.e., number of routes) and investigated how species IARs were influenced by functional traits and environmental factors. We found that species with faster life history traits and reduced flight efficiency had higher IAR intercepts (i.e., locally more stable), whereas migratory species exhibited higher IAR slopes (i.e., a faster gain of stability with increasing spatial scale). In addition, spatial correlation in temperature and vegetation structure synchronized bird population dynamics over space and thus decreased IAR slopes. By demonstrating the joint influence of functional traits and environmental factors on bird population stability across scales, our results highlight the need for dynamic conservation strategies tailored to particular types of species in an era of global environmental changes.Peer reviewe

A diuranium carbide cluster stabilized inside a C80 fullerene cage.

Unsupported non-bridged uranium-carbon double bonds have long been sought after in actinide chemistry as fundamental synthetic targets in the study of actinide-ligand multiple bonding. Here we report that, utilizing Ih(7)-C80 fullerenes as nanocontainers, a diuranium carbide cluster, U=C=U, has been encapsulated and stabilized in the form of UCU@Ih(7)-C80. This endohedral fullerene was prepared utilizing the Krätschmer-Huffman arc discharge method, and was then co-crystallized with nickel(II) octaethylporphyrin (NiII-OEP) to produce UCU@Ih(7)-C80·[NiII-OEP] as single crystals. X-ray diffraction analysis reveals a cage-stabilized, carbide-bridged, bent UCU cluster with unexpectedly short uranium-carbon distances (2.03 Å) indicative of covalent U=C double-bond character. The quantum-chemical results suggest that both U atoms in the UCU unit have formal oxidation state of +5. The structural features of UCU@Ih(7)-C80 and the covalent nature of the U(f1)=C double bonds were further affirmed through various spectroscopic and theoretical analyses